Iím sorry that this post is so long but trying to provide plenty of detail...
Airport Elevation is 3600 feet.
I installed a used IO360-A1A engine on my 7A after having it rebuilt. It has always been hard to get the mixture lean enough at idle. Likewise, after flying and getting the engine hot it idled horribly after landing. Iíve read a lot of articles that made me feel this is normal but a few weeks ago the engine quit on final after pulling it back to idle and I landed about 100 feet short of the runway threshold. The only damage was a totaled threshold light, scuffed paint on the side of my nose wheel fairing, and my ego.
I immediately pulled the entire injection system off of the airplane and sent it to Airflow Performance. They overhauled the whole thing.....servo, flow divider, reduced the size of the restrictors, new injector lines. After installing it wasnít as tough to get the idle leaned although I have a hard time getting a definite 50 rpm rise pulling lean to shutoff. I have a very light 3 blade Catto Prop if that makes a difference. I know the inertia is not as great with a metal prop.
I flew touch and goís to stay in the vicinity of the airport and test the system at all power settings. The first two touch and gos went great. The the third touch and go, I got engine roughness after pulling the throttle to about the 1200 rpm range. I increased the the throttle up a tad to smoothness and forced the plane down. Once I had the runway made, I pulled throttle back to idle. As I was flaring, I could see the prop getting too slow. I slightly increased the throttle and saved the engine from dying. I taxied to the ramp and noticed the hot idle was much better than it had ever been. Some local pilots also commented on how much better it was running.
I taxied to the ramp discouraged by the roughness that I feel would have killed the engine at low rpm. I set the mixture to full rich. I slowly increased the throttle until about 1/2 inch before full throttle where the engine would completely lose power. Just like it was flooding out entirely. This repeated over and over again. Before takeoff, I always have leaned the engine so I didnít know this was an issue. The lean was usually pulled out 1-1/2Ē before takeoff. Engine runs all the way up to full throttle with that setting although the static rpm is only about 2000 rpm on the Catto 3 bladed prop.
When the engine was rebuilt, the mechanic timed the engine. I purchased the piston stop, timing indicator, and mag timing light so I could verify the timing. My engine has a placard calling for 25 degrees before top dead center but I have read where Lycoming moved the spec to 20 degrees. When I checked the actual timing, I am seeing about 18.5 degrees before top dead center.
Would this timing cause the engine to drop out at full power? I am seeing 360-390 degree CHTs. Peak lean shows about 1425 degrees on the EGT.
Please help me to troubleshoot.